The objective of these studies is to describe the mechanisms which regulate the continual exchange of electrolytes between the crystalline lens of the eye and its fluid environment. These mechanisms are responsible for the electrolyte and water balance of the lens which is essential for transparency of the tissue. In this portion of the study we are investigating 1) the role of calcium in regulating lens membrane properties, 2) the activity and distribution of Na-K-activated ATPase in the lens, 3) the relative roles of the lens epithelium and cortical lens fibers in maintaining electrolyte balance, 4) electrical properties of lens membranes, and 5) changes in electrolyte balance during cataract development in rats.